The updated initiative, which includes Illinois, Iowa, Kansas, Michigan, Minnesota, Wisconsin and Manitoba, would establish a cap-and-trade system to curb carbon dioxide emissions 15-25 percent by 2020 and 60-80 percent by 2050, according to this Gannett article. Such a pact already exists in the Northeast.

It is not clear why South Dakota and Ohio, which were represented in the previous accord, are not part of the announcement.